A NEW RESEARCH TOOL THE DIFFERENTIAL THERMOBALANCE

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-04861A000400030007-9
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 6
• Document Creation Date: December 20, 2016
• Document Release Date: June 6, 2006
• Sequence Number: 7
• Publication Date: August 1, 1955
• Content Type: REPORT

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Approved For Release 2007/10/23: CIA-RDP78-04861AO00400030007-
3
A NEW RESEARCH TOOL
THE DIFFERENTIAL THERMOBALANCE
W. L. De Keyser
Bulletin de la Socl6tA Franralse de CAramlq.ue
20 119531 2-5
August 1955
Approved For Release 2007/10/23: CIA-RDP78-04861A000400030007-9
 Approved For Release 2007/10/23: CIA-RDP78-04861A000400030007-9
1.1 RESE H TOOL
The differential thermoba3.ance
W, L.'De KeysB1
Bullet'J_ de l`a Societe' 'ancaise de C~ramique
i
20.. (1953) 2 -''5. .
r=, French)
Ste. The author ha's''devided a, new method of therino-gravimetric
analysis which instead of recording the total loss of weight of a .sample
of temperature p = -f (t) establishes the differential curves
dp
Me precision. of the recording on a' relatively small scale is .equal
to that which would be given by the integral curve traced on a very
large scaled
The curves obtained have the same appearance as those of
differential thermal analysis, but have the advantage over the latter
of having quantitative values.
The author describes an autornatie'-apparatus which allows the
direct establishment of the therrrio-=gravimetric differential curves.
In a recent book, Clement Duval (1)'' has demonstrated the great
interest which can be taken in what he called thezmo-gravimetrio analysis.
There are numerous models of thennobalances for carrying out this
analysis. These instruments vaake it possible to measure or record the
loss of . weight of a sample placed in a furnace.
The loss of weight can be recorded as?a function of the time at
constant. temperature or may be measured for a gradual elevation of the
oven temperature.
Numerous arrangements have been devised, and we have described. ' the
one developed by us when working. on Belgian clays'. (2)
Thermo gravimetric analysis may be compared to thermal analysis
whenever the phenomenon.. caused by elevation of temperature is
accompanied by loss in weight.
.It is particularly useful and interesting in the study of the
decomposition of hydrates and carbonates.
It has the advantage over thermal analysis of having more value
quantitatively, Actually, if the decomposition temperature of a hydrate,
a hydrated silicate or,a carbonate is,known, the loss of weight at this
temperature allows the determination of the weight of.,the..hydrate or the
carbonate contained in the substance analysed.
It was with this aim in view that some years ago we made great use
of the thennobalanoe,in the. study,_of clay : substances. (.2)
For references see end
Approved For Release 2007/10/23: CIA-RDP78-04861A000400030007-9
 Approved For Release 2007/10/23: CIA-RDP78-04861A000400030007-9
We tried at that time to record photographically, but we abandoned
the attempt as we were unable to obtain a large scale diagram in a simple
enough manner, and under these conditions one is forced to use a balance
of low sensitivity or to use very small quantities of materirl?:` In. both
cases precision suffers a great deal.
Further, when a slight loss of weight takes place at a temperature
slightly higher than that of an appreciable loss of weight, the second
phenomenon is not always distinguished, and for this reason we were
held to the tedious method of weighing at intervals of one minute.
In this way it was possible in spite of convection currents in the
furnace and without the latter-hay..ing any Jeffect on the weights, to make
these weighings within a milligram, the $arrple in the Furnace weighing
2.5 grams. In this way we obtained fairly accurate, diagrams.
Under these conditions, the principal loss of weight of a clay
taking place corresponded to a recording dimension of 300 mm. The
inconvenience of graphical representation of this type consists in
producing diagrams which are certainly accurate,:but of very large
dimensions, of which the printed reproduction is"Opractically impossible.:
On the other hand, even when working with a very large sample,
it is sometimes difficult to solve the problem of the determination of
the commencement of dehydration of a hydrate whose decomposition
temperature is fairly close to that of another hydrate.
In order to determine such temperatures a change was-made to
graphic differentiation of the weight loss curves.
Henceforth, the total loss of weight is no longer represented
by the difference between the initial and final ordinates, but at the
area lying between the differential curve and the abscissa.
The result is that without sacrificing accuracy, one can obtain
a diagram of much smaller' d mensions.
On the other hand., the indication of the commencement of
dehydration is much more precise than for the cumulative initial curve.
Thus curve II in figure I represents the differential curve of
loss of weight of a sample of Zettlitz kaolin to which 10 of diaspore
is added.
We are able to distingu.i sh clearly between the beginning. of
dehydration of the ZettlitZ kaolin T, and the beginning of dehydration of
the diaspore T2.
Such a distinction is hardly possible on the initial diagrams, even
when these are drawn on a very large